Stay away from the Black Hills from the last week of July till August 13. The Sturgis motorcycle rally officially runs from Aug 2 to Aug 12, and my one experience, and asking others, is that people show up early but are gone by the mon or tues after the ending day. There will be some 400,000 people in the area for the rally and not something you want to get mixed into while trying to sightsee the Black Hills.
Here is my account of my trip to the Badlands and Black Hills and the Eclipse in August.
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29487108.cfmCharles